1. Field of the Invention
The present invention relates to portable data storage devices and, in particular, to powering up a hard disk drive in a portable data storage device with a limited power supply.
2. Discussion of the Related Art
Large capacity portable storage devices may be used in place of or in addition to conventional hard disk drives which are fixed within the computer housing. Portable storage devices may be coupled to the host computer as a separate drive, i.e., in a drive bay, or as a peripheral device standard interface devices, such as parallel port, PC Card, Universal Serial Bus (USB), and FireWire cables. An example of a portable storage device is described in U.S. Ser. No. 10/222,687, entitled “Data Storage Device”, filed on Aug. 15, 2002, having the same assignee as the present disclosure, and which is incorporated herein by reference.
While standard interface devices, such as interface cables, can transfer data at an adequate rate, typically, these devices are limited in the amount of power that they may transferred through them. The power supply limitation of the interface devices is particularly problematic when the portable storage device uses a hard disk drive. Hard disk drives typically require a relatively large amount of power to start up, i.e., to accelerate the hard disks to the desired rotational speed.
Accordingly, portable storage devices typically include a power supply that is separate from the standard interface device that connects the portable storage device with the computer. While the separate power supply can easily provides enough power to start the hard disk drive, a separate power supply requires additional cable and interconnections as well as a power source, e.g., a power supply within the computer or access to an electrical outlet. The additional cable and interconnections are inconvenient and cumbersome, and access to a power supply, either from the computer or from an electrical outlet, may be limited, e.g., when the portable storage device is used with a lap top computer.
Thus, what is needed is an improved system for starting up a hard disk drive in a portable storage device without requiring a separate power supply.